As a process for the production of iodine pentafluoride by reacting iodine and fluorine, the followings are exemplified: A counter current contacting process of fluorine with iodine dissolved in iodine pentafluoride (see Patent Reference 1); and a bubbling process of fluorine into molten iodine or slurry iodine (see Patent References 2 and 3).
In the above processes, fluorine is supplied to a liquid phase, and sublimation of iodine is accelerated by nitrogen used as a diluting gas for the fluorine supply, unreacted fluorine and the like. As a result, iodine deposits and becomes solid onto an inside of an outlet line of a reactor, which ultimately may lead to clogging of the line. An operation of the reactor at an elevated temperature for the purpose of avoiding such iodine deposition is difficult.
Heat of formation of iodine pentafluoride is as large as 920 kJ/mol, and it is likely that solid iodine depositing to the line reacts with fluorine so that temperature increase locally happens. Thus, those processes are industrially not so useful from a viewpoint of the safety.
In addition, fluorine and iodine are very reactive. When fluorine becomes in contact with concentrated iodine such as the slurry iodine, or the molten iodine, there is a risk in that they react explosively, so that there leads to a risk in that iodine flows back to a fluorine supply line. If fluorine goes back to its supply line, fluorine and iodine reacts in such line, and the temperature in the line is locally and rapidly increased, which leads to a risk in that the line, an apparatus related thereto and the like are damaged.
Particularly, with reaction heat removal by means of sensible heat using an indirect heat exchanger (such as an outside jacket) which is conventionally used for the removal of the reaction heat in a reactor, an amount of heat which can be effectively removed is too small compared with the heat formed by the reaction, so that control of the reaction temperature is difficult. Upon scale-up of the reactor, there is a risk in that runway of the reaction, and further explosion may occur.
Alternatively, there is a process in which a fluorine gas is passed over molten iodine so as to react them, so that a vapor mixture which contains iodine pentafluoride and iodine is obtained, and said vapor mixture and fresh fluorine gas are reacted in the presence of liquid iodine pentafluoride which has been already formed so that iodine pentafluoride is further formed (see Patent Reference 4).
Although this process has an advantage in that the reaction heat is effectively used for keeping iodine in its liquid state, an advanced reaction control technique is required so as to avoid reaction runaway and the explosion due to great heat generation of the reaction. Further, since there is a risk in that line clogging by means of sublime iodine, this process is not necessarily satisfactory for the industrial process.    Patent Reference 1: U.S. Pat. No. 3,367,745    Patent Reference 2: Japanese Patent Kokai Publication No. 65196/1979    Patent Reference 3: G.B. Patent No. 1326130    Patent Reference 4: Japanese Patent Kokai Publication No. 145602/1983